1. Field of the Invention
The present invention relates to a pressure accumulation fuel injection device that supplies fuel from a common rail accumulating high-pressure fuel to an injector and in particular relates to a pressure accumulation fuel injection device that determines an abnormality of a fuel pressure sensing device sensing fuel pressure of the common rail.
2. Description of Related Art
Conventionally, as described in Patent document 1 (JP-A-2008-202593), a pressure accumulation fuel injection device that supplies fuel from a common rail to an injector supplies high-pressure fuel from a high-pressure fuel supply pump to the common rail and controls fuel pressure of the common rail by changing transfer quantity of the fuel from the high-pressure fuel supply pump.
In that case, the fuel injection device senses the fuel pressure of the common rail with a fuel pressure sensing device and controls the transfer quantity of the high-pressure fuel supply pump based on the sensed fuel pressure and target pressure such that a difference between the sensed fuel pressure and the target pressure decreases.
In such the conventional fuel injection device, if the sensed fuel pressure becomes substantially constant pressure due to an abnormality in the fuel pressure sensing device, the fuel injection device becomes unable to control the fuel pressure. In the worst case, there is a possibility that an internal combustion engine stops due to abnormal drop of the fuel pressure or there is a possibility that abnormally high fuel pressure causes failure of devices or fuel leak from fuel pipes or the like, leading to a fire hazard. Therefore, change in the fuel pressure before and after the fuel injection from the injector is sensed with the fuel pressure sensing device. If the pressure change amount is equal to or larger than a predetermined value, it is determined that the fuel pressure sensing device is operating normally. If the pressure change amount is smaller than the predetermined value, it is determined that the fuel pressure sensing device is abnormal and the abnormality is reported.
For example, the injector opens and closes a low-pressure passage extending from a pressure chamber, to which the high-pressure fuel of the common rail is applied, to a low-pressure side. If the low-pressure passage is opened due to energization and thus the fuel pressure in the pressure chamber decreases, a nozzle needle ascends and the injector opens. While the injector is open, the injector leaks the high-pressure fuel, which is supplied from the common rail, to a low-pressure flow passage side through the pressure chamber and therefore generates large quantity of the leaked fuel. Since the large quantity of the fuel leaks from the injector, the fuel pressure largely changes before and after the fuel injection from the injector and the change amount of the fuel pressure sensed by the fuel pressure sensing device increases.
However, the large quantity of the fuel leak causes lowering of a fuel efficiency. If an injector causing little or no fuel leak is used in order to improve the fuel consumption efficiency, it becomes difficult to obtain pressure change equal to or larger than the predetermined value. As a result, there is a possibility that the abnormality detection of the fuel pressure sensing device becomes difficult or erroneous determination is induced.